1. Field of the Invention
The invention relates to conveyor assemblies and, more particularly, relates to a conveyor assembly that includes a swivel wheel diverter for selectively diverting conveyed articles at an angle from a conveyor. The invention relates additionally to an improved diverter wheel assembly usable in a diverter and to an improved method of diverting articles from a conveyor.
2. Discussion of the Related Art
It is necessary in many conveying applications to selectively and alternatively 1) convey articles along a conveyor in an initial conveying path or direction (generally known as "in-line" conveyance) and 2) divert articles from the conveyor and onto another conveyor, a sort location, a spur line, etc. Selectively operable apparatus usable for this purpose are generally known in the art as "diverters."
One type of diverter used in a variety of applications and particular in high-speed applications is the so-called wheel diverter that uses a series of rotating diverter wheels to direct articles. The diverter wheels of traditional wheel diverters at least selectively rotate at an angle to the in-line direction of conveyance of the primary conveyor in which the diverter is disposed and are positioned between adjacent primary conveyor sections (or, in the case of a roller conveyor, between adjacent rollers) so as to selectively engage and divert articles travelling along the conveyor. To effect a divert operation, the diverter wheels of a diverter may swivel, pop-up, or both swivel and pop-up.
In diverters in which the diverter wheels pop-up, the diverter wheels are normally positioned beneath the primary conveyor's plane of conveyance. These wheels are permanently skewed and hence cannot rotate in-line with the associated primary conveyor. To effect a divert operation, the skewed wheels are driven upwardly so that they "pop-up" into the plane of conveyance to convey articles away from the primary conveyor. Diverters of this type are disclosed in U.S. Pat. No. 3,138,238 to Good et al.; U.S. Pat. No. 3,983,988 to Maxted et al.; and U.S. Pat. No. 4,328,889 to Maxted.
Other diverters incorporate diverter wheels that can swivel but do not pop-up, at least on a cycle-to-cycle basis, but that instead swivel between an in-line orientation and a skewed orientation in which they rotate at least generally towards a secondary conveyor or some other device extending at an angle from the primary conveyor. A diverter of this type is disclosed in U.S. Pat. No. 5,117,961 to Nicholson.
Still other diverters incorporate diverter wheels that both pop-up and swivel. The diverter wheels of these diverters can be swiveled from an in-line orientation in which they help convey articles along the primary conveyor to a skewed orientation in which they convey articles at an angle from the primary conveyor. The diverter wheels pop-up as they swivel so that they may facilitate a diverting operation by lifting the article from the primary conveyor and positioning it for transfer to a secondary conveyor or another structure that may be located above the plane of conveyance of the primary conveyor. Lifting the article from the primary conveyor prevents the adjacent portions of the primary conveyor from acting on the article and hence prevents the diverted articles from being pulled in two directions at once. Diverters having diverter wheels that both pop-up and swivel are disclosed in U.S. Pat. No. 4,598,815 to Adama; U.S. Pat. No. 4,703,844 to Jahns; and U.S. Pat. No. 5,029,693 to Williams.
The rotational speed of the diverter wheels of the diverters disclosed in several of the above-mentioned patents are controlled to be different from the in-line speed of the primary conveyor. For instance, the diverter wheels disclosed in the Maxted '988 and Nicholson patents rotate faster than the in-line speed of the primary conveyor to accelerate articles being diverted to maintain a desired spacing between diverted articles. The diverter wheels disclosed in the Berends patent are somewhat more sophisticated in that the diverter wheels are accelerated only during a diverting operation so that they convey articles at generally the in-line speed of the primary conveyor when in their in-line orientation and accelerate articles when in their skewed orientation. The increased speed of the skewed diverter wheels is said to allow the articles to be diverted abruptly from the main or primary conveyor without interference from either the previously-diverted articles or the upstream articles. Diverter wheel acceleration is effected by driving each wheel directly via a drive shaft that rides up a curved surface of a spool upon wheel swiveling to increase the rotational velocity of the shaft and hence the rotational velocity of the wheel.
Previously-known wheel diverters of the type described above exhibit several drawbacks and disadvantages.
For instance, none of the diverters described above is capable of changing the rotational speeds of diverter wheels between two distinct, pre-settable speeds upon diverter wheel swiveling. Interaction between the curved spool surface and the drive shaft of each diverter wheel described in the Berends patent instead causes the rotational velocity of the diverter wheel to vary progressively as the wheel swivels and its shaft rides up the curved surface of the associated spool. In addition, the direct contact between the drive shaft and the spool in Berends' diverter may result in accelerated wear of both components.
In addition, none of the prior art diverters, including that disclosed by Berends, controls the rotational velocities of the diverted wheels such that the velocity of the wheels increases progressively from wheel-to-wheel as one travels laterally across the primary conveyor. Rather, all diverter wheels rotate at the same velocity when in their diverted position. As a result, article diverting is effected solely via diverter wheel skewing. There is no change of speed across the width of the article that otherwise could assist article diverting by turning the article towards the secondary conveyor.
In addition, in those prior art diverters in which the diverter wheel is driven by an O-ring or some other type of belt (generally considered to be the most cost effective and efficient manner of driving a diverter wheel) and in which the diverter wheels both swivel and pop-up, the belt stretches twice. It stretches first as the diverter wheel swivels due to the change in angular orientation between the driven diverter wheel and the pulley or spool which drives it. It stretches again during the pop-up operation because the vertical spacing between the rising diverter wheel and the vertically-stationary drive pulley increases. This two-stage stretching (both stages of which may take place simultaneously if the swivel and pop-up operations occur simultaneously) may lead to premature wear and early failure of the driven belt.
Moreover, no known pop-up diverter smoothly ramps the diverted articles upwardly from the surface of the primary conveyor. The diverted articles instead are lifted rather abruptly by the elevated diverter wheels.